The Program Project Grant is organized into four projects with seven supporting core laboratories: 1. Cholesterol Lowering Atherosclerosis Study I (CLAS I) - this is a clinical trial of lipid lowering in atherosclerosis regression/progression. It is planned as a first of a series which uses arterial imaging to evaluate results of lipid level reduction alone or in combination with alteration of other risk factors. The acronym, CLAS I, has been designated to allow easy identification in discussing the project with potential volunteers. 2. Carotid Ultrasound Imaging - this project will employ commercially available ultrasound imaging devices to evaluate carotid arteries in the subjects participating in CLAS I. 3. Visualization of Branch Junctions and Flow Through Branch Junctions - this study is closely coupled to research in progress supported by NASA under the auspices of the Medical Image Analysis Facility. Its long-range goal is to visualize the morphology of branch junctions which produces flow disturbances of clinical significance in atherogenesis. 4. Hypoxia of Arterial Wall at Branch Junctions and Bifurcations - this project is designed to test the hypothesis that hypoxia of the arterial wall plays a role in the development of atherosclerosis, in particular in the regions of branches and bifurcations. Core Laboratories include Administration, Lipid, Smoking Metabolite, Image Processing, Angiographic, Biostatistical, and Research Angiographic.